The present invention is particularly intended for use on commercial vehicles, although it may be used with any internal combustion engine connected to a fuel tank having a draw and return tube assembly. In particular, diesel engines typically operate by drawing fuel from a fuel tank, combusting a portion of the fuel and then returning the unused, or uncombusted, fuel to the fuel tank. The volume of fuel returned to the fuel tank is dependent on engine power output, and generally is quite substantial. Accordingly, such draw and return tube assemblies play a vital role in the operation of diesel engines.
Heavy commercial vehicles frequently employ dual fuel tanks, also called saddle tanks, wherein fuel is drawn simultaneously from both tanks for combustion within the engine. To prevent uneven draw and return of the fuel, which may lead to air being drawn into the engine, fuel flow regulators, such as draw and return tube assemblies, typically are installed in each of the dual fuel tanks. One prior art draw and return tube assembly comprises draw and return tubes connected to a flange at one end and connected together by a bracket at another end opposite the flange. The flange typically is mounted at an aperture sized to receive the flange on an outside surface of the fuel tank such that the opposite, bracketed end of the tubes extends downwardly into fuel held within the lower portion of the tank. Draw and return lines from the engine are connected to the draw and return tubes at the flange.
The tube openings opposite the flange typically extend away from one another and are each positioned an equal distance from the flange so that the draw and return tube fuel openings are also each positioned an equal distance below the top surface of fuel held within the tank. In this arrangement, when the two saddle tanks and the corresponding draw and return tube assemblies are each positioned on the commercial vehicle, the pressure head of fuel positioned above the draw and return tube openings of each assembly will result in equal amounts of fuel being withdraw from each of the tanks and equal amounts of fuel being returned to each of the tanks. In addition, swedging or crimping of the end of the return tube opening opposite the flange will facilitate filling the return fuel line. This filling of the return fuel line enables a siphon effect between the left and right hand fuel tanks. Accordingly, the draw and return tube assemblies of the prior art act as passive flow regulators for ensuring equal levels of fuel drawn and returned to each of the two saddle fuel tanks.
Conventional draw and return tubes, at their ends opposite the flange, typically are bent at a ninety degree angle away from each other such that the open ends of the tubes opposite the flange are spaced apart from each other a distance of at least twelve inches and such that the return flow of fuel into the tank is in a direction opposite to the draw tube opening. Separation of the draw and return tube openings helps to ensure that heated and aerated fuel returned to the tank through the return tube is not immediately redrawn into the draw tube but is instead cooled and deareated by the remaining fuel held in the fuel tank.
This bent configuration of the draw and return tube assembly results in a cross section of the assembly that prohibits placement of the assembly through the flange-sized aperture of the tank once the tank has been manufactured. Accordingly, due to the large cross section of the assembly, assemblies of the prior art must be placed within an interior of the tank and installed therein prior to final assembly of the tank. Assembly of the tank, therefore, requires the step of partial completion of the tank, installation of the draw and return tube assembly, and then completion of the tank. This process can be quite time consuming and costly. Moreover, once installed, prior art draw and return tube assemblies cannot be removed or repaired if the assemblies become damaged or clogged. In addition, there is a variety of different sized draw and return tube assemblies that may be installed in a tank. Tank manufacturers may desire to have an inventory of fully assembled fuel tanks on hand wherein the desired size draw and return tube assembly is installed within a tank when requested by a customer. Installation of a draw and return tube assembly into a completed tank, in response to a request for a particular size draw and return tube assembly, is not feasible with the large cross section assemblies of the prior art.
The process of manufacturing a conventional draw and return tube assembly typically involves cutting the tubing to a particular length, bending the tubing at the ends opposite the flange, securing the tubing to the flange, and then stabilizing the assembly by placing a bracket on the tubes at the end opposite the flange. The bracket typically is a three-piece device having two clamp plates and a fastener, such as a rivet. The bracket is installed by placing the clamp plates around the tubes, placing the rivet through aligned apertures in the clamp plates and then fastening the plates in place by clinching the rivet. This can be a labor intensive and time consuming process. Moreover, during typical driving conditions for a commercial vehicle, the bracket may loosen on the tubes such that the bracket falls to the bottom of the fuel tank. Due to the permanent installation of the draw and return tube assembly, the assembly cannot be removed to repair the loosened bracket, thereby requiring replacement of the entire fuel tank.
Accordingly, there is a need for a draw and return tube assembly that may be installed within a fuel tank after the fuel tank has been completely manufactured. Moreover, there is a need for a draw and return tube assembly that does not include a bracket and which may be manufactured without the labor intensive step of securing such a bracket to the tubes.